1. Field of the Invention
The invention relates to a method for configuring a composite drive for a disk drive array controller, and more particularly, to a method for configuring a composite drive for a disk drive array controller which combines data, a first portion of which is unique to each disk drive comprising part of the composite drive and a second portion of which is common to all disk drives forming the composite drive, stored by the disk drives together with data stored by the disk drive array controller to configure the composite drive.
2. Description of Related Art
A disk drive controller is a peripheral interface unit, typically installed on an expansion bus for a computer system, which converts input/output (or "I/O") read and write requests into a sequence of seeks, delays and data transfer operations in which data is read from or stored to a disk drive coupled thereto. A disk drive array controller performs similar tasks for a set of disk drives coupled thereto. However, the disk drive array controller does not differ from a simple disk drive controller merely in the number of disk drives for which it performs such operations. More importantly, the disk drive array controller differs from the disk drive controller in that, with respect to the disk drive array controller, the set of disk drives coupled thereto emulate a single disk drive having a greater capacity and higher performance characteristics than any individual disk drive included as a portion thereof. This large, higher performance disk drive emulated by the set of disk drives is referred to as a "composite" drive. To perform an access to a specified location within the composite drive, the disk drive array controller must know both the position of the particular disk drive to be accessed, as well as the location within that disk drive, which corresponds to the composite drive location for which access is sought.
As one skilled in the art should readily appreciate, the replacement and/or substitution of disk drives is appreciably simpler for a disk drive controller than for a disk drive array controller. As the disk drive controller views a disk drive in its entirety, a replacement disk drive can be coupled to the controller and, provided necessary information regarding the configuration of the disk drive is provided to the disk drive controller, the disk drive controller will be able to immediately access the replacement disk drive. Similarly, a user can move a disk drive to a new disk drive controller without losing any data on the disk drive. For disk drive array controllers, however, disk drives are typically installed at specific positions or "slots" on a common bus or buses and, when the disk drive array controller configures the set of disk drives forming the composite drive, the disk drive array controller will memorize the identity, position and use for each of the disk drives. This information is then provided to each disk drive. Accordingly, after configuration is complete, each disk drive knows its particular location within a composite drive. However, if one of the disk drives is then moved to a different location, that disk drive will no longer know its location within the composite drive. As a result, the user is not always able to immediately use the disk drive after it has been moved. In addition, loss of data may also occur when the disk drive is moved.
It can be readily seen from the foregoing that it would be desirable to store all of the information which describes both the composite drive and a particular disk drive which forms a portion of the composite drive on the disk drive itself so that, when the drive is moved, the information needed to configure the disk drive moves with the drive itself. Accordingly, it is an object of the present invention to provide a method for configuring a composite drive for a disk drive array controller which enhances the ability of a user to remove, replace or otherwise move the disk drives which comprise the composite drive.